Thermostatic control for vapor electric devices



Dec. 26, 1933- P. M. CURRIER 1,941,339

THERMOSTATIC CONTROL FOR- VAPOR ELECTRIC DEVICES Origina; Fild June 24, 1931 Inventor: Philip mCurrieY3 k M av /ja His Attornev.

Patented Dec. 26, 1933 UNITED STATES THERMOSTATIC CONTROL FOR VAPOR ELECTRIC DEVICES Philip M. Currier, Ballston Lake, N. Y., assignor to General Electric Company, a corporation of New York Application June 24, 1931, Serial No. 546,651

Renewed May 29, 1933 Claims. (01. 236-1) The present invention relates to vapor electric apparatus of the hot-cathode type, i. e. to devices which employ cathodes of the directly and indirectly heated type, as distinguished from the- 5 pool form of cathode. The invention is directed more particularly to the feature of maintaining the vapor pressure of such devices substantially constant regardless oi changes in ambient condition.

Devices of this; character may be subjected during operation to severe changes of ambient condition, for example, seasonal changes, also variable room temperatures which cause ,the temperature of the envelope to vary and to change the pressure of the contained vapor. This action, unless compensated, may deleteriously afiect the operation of the device to the extent in some cases of causing arc-back or at least, of severely limiting the current carrying capacity of the tube, as well as introducing other undesirable effects. An arrangement for maintaining the temperature of the envelope, or rather certain portions thereof, as will appear hereinafter, substantially constant, is therefore extremely desirable.

It is found that vapor devices which contain hot or thermionic cathodes, and which may or may not employ an electrostatic control element inaddition to the usual anode, lend themselves particularly well to thermostatic regulation. In operation, the vapor is continually going through the process of condensation and re-evaporation during which the temperature of the coolest portion of the envelope on which the vapor condenses determines the vapor pressure in the whole envelope.

An object of the present invention is to provide an accessory to bring about an automatic control of the temperature of certain portions of the envelope, thereby to maintain the vapor pressure constant. In carrying out this object, I prow pose to regulate the temperature of the coolest" envelope portion or portions by subjecting them to a fluid-whose temperature automatically is controlled and maintained constant. The invention will be better understood when reference is made to the following description and the accompanying drawing which shows a diagrammatic representation of the improved device.

In the drawing, numerals 1, 2 and 3 designate various types of hot-cathode arc discharge devices which employ vapor as the ionizable medium, usually mercury, on account of its relatively low ionizing potential. Each device containsa thermionic cathode, directly or indirectly heated,

an anode, also an electrostatic control member or grid for controlling the initiation of the arc. These electrodes are indicated generally by the dotted and light lines. Alternating current is usually supplied to the anode circuit of each device and a direct current or alternating current voltage to the control member for determining the point in each cycle at which the arc is'to start. After the arc is started the grid loses control and the anode current may be stopped by 35 removing the anode voltage, as for example, when it passes through the zero point of the cycle. The output of these devices consists of rectified current, generally of many amperes whose average value over a period 01 time is determined by a relatively small voltage applied to the grid. Devices of this character have been described by A. W. Hull in the General Electric Review, Vol. 32, No. 2, April, 1929, pages 213 to 223 inclusive, and further description is unnecessary other than to state that their efiicacy of operation is dependent upon the maintenance of a constant predetermined vapor pressure under all conditions, which in turn is dependent uponthe temperature of the coolest portion of the envelope where the 30 condensation and reevaporation of the mercury takes place. These devices may be employed,- ior example, as sensitive relays for controlling large currents or positioned in places subject to extreme variation of temperature as when ex- 35 posed alternately to sunlight and darkness, or to summer and winter conditions so that some form of temperature regulator is necessary.

In accordance with my invention, I propose to maintain the coolestportion of each envelope'at a constant predetermined temperature by directing thereon a stream of air or other fluid under pressure, and at the proper temperature. As shown in the figure, the air is projected through one or more nozzles or conduits 4 directed toward 5 the respective coolest portions of each envelope. The number and shape of nozzles in each case depends upon the amount of liquid or condensed mercury whose temperature is to be controlled, also upon the extent of the mercury surface 0 available for temperature regulation.

In the type of device exemplified by the diagram 1, the mercury is contained at the bottom of a tubular member, and I have" indicated the air duct as taking a general U-shape with sev- 5 eral openings spaced along each leg. In the device designated by reference character 2, the mercury is also contained at the bottom of the device, but consists of a body of greater content than that shown in the device 1. In this case I have indicated the fluid-directing system as taking the form of a'pair' of nozzles branched 'ifrom themain conduit 7. Thedevice exemplified by diagram 3 is provided with a side tube removed from the main portion of the envelope, which tube is designed to be the coolestportion of the envelope where the mercury condenses. One nozzle may be suflicient in this case to direct the temperature-controlling fluid against the side.

tube. As shown, the air is directed against that portion or portions of each device which controls the rate of condensation and reevaporation of the mercury, thereby to control the pressure of the vapor contained within each device.

The air or other fluid may be obtained from a reservoir which conveniently consists of a rectangular box 5 closed on all sides exceptior two large openings, one of which communicates with a high pressure blower 6 of any suitable and well known design, and the other of which is located on the opposite side and connected to the main air duct '7. If desired, a bafile plate 8 may be provided between the two openings so as to ensure a thorough circulation of the fluid within the box. Cool air is admitted to the blower in the usual manner. The box is also provided with a heater 9 indicated diagrammatically as two serially connected coils of resistance wire, also a thermostatic relay 10 of any suitable and well-known type. The heater. may be energized by alternating or direct current which is conducted through a movable contact member 11 under the control of an electromagnet 12. The latter is connected in series with the thermostatic relay, across the line.

In operation, the thermostat is set to respond to a definite temperature, determined by the temperature which it is desired to maintain at the coolest portion of each envelope. When the temperature of the air in the box as delivered by the blower becomes less than the temperature for which the thermostat is set, as for example, when the ambient temperature becomes less, the thermostat operates to close the circuit of the electromagnet, which upon being energized, causes the heater circuit to close. The heater serves to raise the temperature of the fluid moving through the reservoir and the fluid, in a heated condition,

is caused to impinge against the selected portions of each envelope. When the ambient temperature becomes higher than the temperature which causes the actuation of the thermostat, the latter automatically opens and causes deenergization o! the electromagnet and heater, thus allowing air in the cool and unheated state to be supplied to the nozzle by the blower. In order for the regulation to be effective under all conditions, it is evident that the coolest portion of the envelope durdense. To insure this condition when the normal ambient-temperature is so high as to preclude vapor condensation, it may be necessary to cool the air delivered by the blower to a temperature below that of ambient or room temperature; A suitable arrangement for this purpose may take the form of a cooling coil 13 positioned near the outlet of the blower, and containing passageways for a fluid whose temperature normally is below that of the ambient temperature; a convenient fluid for this purpose is tap water. The operation of the improved apparatus is therefore such as r to supply heated, unheated or cooled air to the envelope portions, depending upon whether these portions tend to become-cooler or hotter than the predetermined temperature, thus maintaining them at a constant predetermined temperature. Hence, by maintaining the rate of condensation and reevaporation of the mercury atthese selected envelope portions, the improved device causes the vapor pressure in each envelope to remain substantially constant under all conditions which tend to change the pressure, and insures uniformity of operation of each device. v

Hull application, Serial No. 539,695, filed May 25, 1931, andentitled Thermostatic control'ior thermionic arc discharge devices" and assigned to the same assignee as the present application, contains broad claims on the feature of automatically maintaining the temperature of a selected envelope portion of'an electrical discharge device containinga vaporizable material, at a predetermined value regardless of ambient temperature variations.

What I claim as new and desire to secure by Letters Patent of the United States is:-

1. In a temperature regulator for hot-cathode arc discharge devices which employ vapor for the ionizable medium, a portion of the envelope of each of said devices operating at a temperature sufiiciently high to maintain the ionizable medium ina vaporous condition and another portion of the envelope operating at a temperature sufficiently low to cause condensation of a portion of the vapor, means for maintaining the vapor pressure within the envelope substantially constant regardless of ambient temperature changes, said means comprising a closed chamber containing a fluid under pressure and whose temperature is automatically maintained constant under all conditions of ambient temperature, and means for supplying the fluid only to the region of the'envelope where the vapor condenses.

2. In a temperature regulator for hot-cathode arc discharge devices which employ a vapor tor medium in a vaporous condition and another portion of the envelope operating at a tempera .ture sufllciently low to cause condensation of a portion of the vapor, means ior maintaining the vapor pressure within the envelope substantially constant regardless of ambient temperature changes, said means comprising a closed chamber containing a fluid under pressure, a heater in said chamber, and a device for automatically energizing the heater when the temperature of the fluid tends to become less than a predetermined temperature whereby the temperature of the fluid is maintained relatively constant. under all conditions of ambient temperature, and means for supplying the fluid only to the region of the envelope where the vapor condenses.

3. In a temperature regulator for hot-cathodearc discharge devices which employ a vapor for the ionizable medium, a portion of the envelope oi. each of said devices operating at a temperature sufliciently highto maintain the ionizable medium in a vaporous condition and another portion of the envelope operating ataztemperature sufficiently low to cause condensation of a portion of the vapor, means for maintaining the vapor pressure within the envelope substantially constant regardless of ambient temperature changes, said means comprising a closed cham ber containing a fluid under pressure and whose temperature is automatically maintained con,-

stant' under all conditions of ambient temperature, and means comprising a conduit which terminates in a nozzle for directing the fluid against only the portion of the envelope where the vapor condenses.

4. A temperature regulator for hot-cathode arc discharge devices which employ a vapor for the ionizable medium, a portion of the envelope of each of said devices operating at a temperaturesufliciently high to maintain 'the ionizable medium in a vaporous condition and another portion of the envelope operating at a temperature sumciently low to cause condensation of a por-' withstanding changes of ambient temperature.

5. A temperature regulator for hot-cathode arc discharge devices which employ a vapor for the ionizable medium, a portion of the envelope of each oi. said devices operating at a temperature sufliciently high to maintain the ionizable medium in a vaporous condition and another portion of the envelope operating ata temperature sumciently low to cause condensation of a portion of the vapor, means formaintaining the vapor pressure substantially constant regardless of ambient temperature changes, said means comprising a closed chamber containing a fluid under pressure, heating and cooling coils in said chamber, means for automatically energizing the heating coil when the temperature of the fluid within the chamber becomes less than a predetermined temperature, and means for supplying the fluid only to the region or the envelope where the vapor condenses.

PHILIP M. CURRIER. 

